High vapor pressure hydrocarbon products are currently tested for corrosive contaminates using ASTM D-1838—Standard Test Method for Copper Strip Corrosion by LPG or other high vapor pressure hydrocarbon products. See FIG. 2. This involves using a specified test cylinder with a single cavity cylinder provided with a dip tube for venting some liquid from the cylinder (to prevent excessive pressure in the cylinder whenever the liquid-filled cylinder is warmed up) and a hook for hanging a copper strip in the remaining sample of the liquid LPG product or other high vapor pressure hydrocarbon products.
The procedure for collecting the sample and conducting the test are carefully defined in the standard, but once the sample has been caught and a portion of the liquid has been vented to the atmosphere using the dip tube, the test basically requires the cylinder containing the remaining liquid sample and the copper strip to remain in a water bath at 100 degrees Fahrenheit for one hour. The copper strip is highly polished before being inserted into the cylinder and should remain immersed in the liquid product during the test period.
Following the test period, the cylinder is de-pressured, then opened, so that the copper strip can be removed and examined. The strip is graded, depending on the degree and type of discoloration, by comparing the discoloration to a comparator chart, also specified by ASTM. Number 1 copper strips are generally considered acceptable in the industry (non-corrosive), but strips graded to be number 2 or higher are generally considered to be corrosive and off-spec.
The prior art system and method for testing has the unacceptable feature of hydrocarbons being released to the atmosphere immediately after the liquid sample is collected in the cylinder. The purpose of the venting is to provide some outage and prevent over-pressuring a liquid-filled cylinder if the ambient temperature is warmer than the cylinder containing the sample or when the cylinder is immersed in the 100 degree Fahrenheit water bath called for by the test procedure. This is particularly dangerous if there are nearby ignition sources, but constitutes an environmental issue as well. It is also unsafe if the hydrocarbons are contaminated with hydrogen sulfide or other poisonous gases.
ASTM Standard D1267-12 specifies a dual chamber test apparatus. However, this is a test for vapor pressure and is not usable with the test strips needed for corrosion testing.
What is needed is a test apparatus and method that prevents the venting of volatile samples into the atmosphere near the point where the sample was collected, especially if the discharge is into the ambient air, near an ignition source, or near personnel (such as in refinery, terminal, pipeline installation or natural gas processing plant operating areas where the samples are usually collected).
Further, what is needed is a test apparatus and method that provides for the safe expansion of the hydrocarbon sample in the event the test cylinder containing the sample is warmed up by the sun or the ambient temperature after the sample is collected, or when the sample is intentionally heated in the 100 degree Fahrenheit water bath required by the copper strip corrosion test method itself.